Frequency differences between a solar model calibrated with MESA and observations of low-degree modes (ℓ ≤ 3) by BiSON. The lines show fits made using an inverse term (dashed), cubic term (dotted) or both terms (solid). The relative performances of the fits is the same as Fig. 1. The dot-dashed lines show a power law, fit to nine radial orders about ν_max = 3090μHz, as is used in the frequency correction proposed by Kjeldsen et al. (2008).